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1998 Chev Express ecm-b fuse problem
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justrussell
New User
Nov 14, 2007, 7:11 AM
Post #1 of 4
(3574 views)
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1998 Chev Express ecm-b fuse problem
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Hello all, great board,
I've been having problems with my van for many months now, and I'm about ready to push it into the river.
Problem: ecm-b fuse blows without warning while driving, or even sitting at idle. After, you can change the fuse 10 times and when cranked, it instantly blows. I pay to have it towed to the auto electric shop, they pop a fuse in and it runs fine! They can't fix what isn't broken... that will last for anywere from a day to a month, then boom all over again. Originally, I thought it was the fuel pump, so I changed it. The next time, had it towed to the shop, they changed the fuel pump again as they said it must have been defective. 3rd and 4th time had it towed to auto electric places, neither could diagnosis the problem. Now I've had it towed to my house.
I've figured out that the ecm-b has constant power without regard to the key switch. It runs from the underhood fuse box to the ecm. I took off this wiring harness from ecm and tested for continuity between pin on connector and fuse socket, no problems there. I went under van and tried to follow what wiring i could find from fuel pump up and couldn't see anything wrong, but ? Also, when I changed fuel pump originally, I installed a "trap door" to access the fuel pump from inside the van. I've looked at this wiring, and it looks good.
I would really appreciate any help or suggestions anyone could give me.
Thanks.... Russell
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kansasfarmer
Anonymous Poster
farmerboy682003@yahoo.com
Nov 21, 2007, 7:55 PM
Post #2 of 4
(3553 views)
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Re: 1998 Chev Express ecm-b fuse problem
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My 1997 Chevy K3500 has just started doing the same thing. It sounds exactly like the problem you are having. I heard yesterday that perhaps I should have changed some of the wiring to the fuel pump. I put a piece of baling wire where the fuse should be and all it would do was get hot. Towed the worthless piece of s..t to the shop, the mechanic puts a fuse in and bang it starts. Brought it home today and it conked out feeding cattle this evening, put a fuse in and as near as I can tell it did not blow, but the truck will still not start.
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DanD
Veteran
/ Moderator
Nov 22, 2007, 6:02 AM
Post #3 of 4
(3550 views)
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Re: 1998 Chev Express ecm-b fuse problem
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This is just a guess but try unplugging the oil pressure switch? This switch has two functions one (the obvious) sends a signal to the oil pressure gauge/light. Its other job is to act as a back-up means of turning on the fuel pump, if the fuel pump relay fails. The switch is feed power from the ECM-B fuse and is a mechanical switch that may have an internal intermittent short to ground.
The switch will have a three-wire connector; tan for the gauge, orange power feed from the fuse and gray feed to the fuel pump.
The switch closes, supplying power to the fuel pump after the engine builds oil pressure.
Also check the wiring harness leaving the switch; making sure that it has not become pinched or melted on an engine component or engine cover.
Dan.
Canadian "EH"
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justrussell
New User
Nov 22, 2007, 11:28 PM
Post #4 of 4
(3544 views)
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Re: 1998 Chev Express ecm-b fuse problem
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Thanks for the Reply: A few days ago I finally located a complete wiring diagram for my van. Traced the whole circuit and came to the same conclusion. Bought and installed a new oil pressure switch, and just for kicks a new fuel pump relay. I also pulled my fuel pump again to make sure there wasn't anything in my tank that could clog the prefilter and make pump pull bunch (it was clean). Anyway, so far, so good. Been driving it every day, but still have in my mind that any second now it could go. I prefer to find something wrong, fix it and it's fixed. I do hope it was that oil pressure switch!
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